The impact of climate change on the water quality of the Rhine river

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(1)BTO 2006.056(s) 1 september 2006. The impact of climate change on the water quality of the Rhine River.

(2) BTO 2006.056(s) 1 september 2006. The impact of climate change on the water quality of the Rhine River. © 2006 Kiwa Water Research Alle rechten voorbehouden. Niets uit deze uitgave mag worden verveelvoudigd, opgeslagen in een geautomatiseerd gegevensbestand, of openbaar gemaakt, in enige vorm of op enige wijze, hetzij elektronisch, mechanisch, door fotokopieën, opnamen, of enig andere manier, zonder voorafgaande schriftelijke toestemming van de uitgever.. Kiwa Water Research Groningenhaven 7 Postbus 1072 3430 BB Nieuwegein Tel. 030 606 95 11 Fax 030 606 11 65 www.kiwawaterresearch.eu.

(3) Colofon Titel The impact of climate change on the water quality of the Rhine River Projectnummer 11.1614.030 Projectmanager Harmke van Oenen Opdrachtgever Kwaliteitsborger(s) Dr. J.J.G. Zwolsman; Drs. A. Doomen Auteur(s) A.J. van Bokhoven. Dit rapport is verspreid onder BTO-participanten en is openbaar.

(4) The impact of climate change on the water quality of the Rhine River © Kiwa Water Research -1-. BTO 2006.056(s) 1 september 2006.

(5) Preface In front of you is lying the report belonging to a six-month’s traineeship at KIWA Water Research. The traineeship is part of the MSc program of Utrecht University, department of Physical Geography. During my study, the main course was directed to coastal areas and river dynamics. Next to that, all Physical Geographers are interested in the world of many natural and environmental processes. Therefore, when looking for a traineeship, I focused my search on a subject that was related to river dynamics and natural processes. Not long after the start of my search, I found the Company KIWA Water Research at Nieuwegein. The company KIWA Water Research offered me an interesting traineeship related to river dynamics and climate change, it was an offer I could not refuse! The combination, of the worldly minded and very interesting subject of climate change, projected on the river that I am most attracted to, made the time fly. The study that I accomplished at the company KIWA Water Research, is part of a bigger research program. Together with my colleagues Barend de Jong and Antoinella Domnişoru we worked on the subject of ‘the possible effects of climate change on water quality’. Antoinella Domnişoru did a study about the possible effects of climate change on the long term. Barend de Jong focused his research on the possible effects of climate change on the water quality of rivers in general and I, Ad van Bokhoven, did the study about the effects of climate change on the water quality of the Rhine River. To do this, it was necessary to gather many data. The largest part of the dataset that is analyzed, has been delivered by RIWARhine and the websites www.waterbase.nl; www.aqualarm.nl and www.helpdeskwater.nl. Without their tremendous services, it was not possible to analyze possible impacts of climate change in the Rhine catchment. During this period of six months, the three of us had interesting discussions and conversations, especially on the subject climate change, but also about our normal lives and activities. Therefore and for the support during the hard work, I like to thank you both. Next to Barend and Antoinella, I would like to thank my supervisors Annette Doomen and Gertjan Zwolsman from Kiwa Water Research, because they were very important in guiding and developing the report. They gave me the freedom to make mistakes and to develop myself once again. At last, I would like to thank my supervisor from the University Of Utrecht, Hans Middelkoop, for helping to improve the report and for leading my traineeship.. The impact of climate change on the water quality of the Rhine River © Kiwa Water Research - 2-. BTO 2006.056(s) 1 september 2006.

(6) The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. -3-. BTO 2006.056(s) 1 September 2006.

(7) Abstract It is recognized that climate change will affect the discharge regime of the Rhine River. Especially the anticipated increase in extreme river discharges (floods and droughts) poses serious problems to water management authorities, both with regard to water quantity and water quality aspects. Water quality effects of climate change are not sufficiently recognized, although there are indications that this may become a serious problem in the future. In this research the effect of hydrological extremes on water quality are studied for the Rhine River, in order to assess potential water quality effects of climate change. The water quality of the Rhine was studied for the periods 1975-1977 and 1987-2005. During these periods eight hydrological extremes occurred, five of which being classified as floods and three as periods of drought. The water quality during these hydrological extremes has been compared with the water quality in reference periods before and after the events. In total, fourty-one water quality parameters have been investigated, comprising general variables (e.g. temperature, suspended matter, dissolved oxygen), major ions, nutrients, heavy metals and metalloids, PAH’s, pesticides and other organic micro pollutants. Due to this analysis, important consequences of decreasing river flow in combination with high temperatures as well as the consequences of river floods on water quality has been obtained. The results show that water quality during hydrological extremes is most of the time different from water quality during mean hydrological circumstances. For example, during the summers of periods of drought water temperatures are higher then normally. In addition, concentrations of chlorophyll-A, concentration of the investigated major ions, concentration of the investigated heavy metals and metalloids are increased during periods of drought. During flood events, the concentrations of suspended solids and all adsorbed chemicals (heavy metals, organic micro pollutants and pathogens) are increased. It is concluded that the summers of 1976 and 2003, which were exceptionally dry, and the floods of 1988, 1993, 1995, 1998 and 2003, may serve as a preview of the effects of ongoing climate change on water quality. In addition, some empirical relations between substances and river discharge or relations between substances and temperature have been derived, which can be used to predict future concentrations during hydrological extremes.. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. -4-. BTO 2006.056(s) 1 September 2006.


(9) Part one: potential effects of climate change on the Rhine catchment. INTRODUCTION ........................................................................................................................... - 14 1.. CLIMATE AND WATER QUALITY................................................................................... - 18 1.1 WATER TEMPERATURE ..............................................................................................................- 22 1.2 RIVER DISCHARGE AND SEA LEVEL RISE ....................................................................................- 23 1.3 CHEMICAL LOADINGS ................................................................................................................- 24 -. 2.. THE RHINE CATCHMENT AREA AND PRESENT CLIMATE .................................... - 28 2.1 TOPOGRAPHY ............................................................................................................................- 28 2.2 PRESENT CLIMATE IN THE RHINE CATCHMENT ..........................................................................- 29 2.3 DISCHARGE CHARACTERISTICS ..................................................................................................- 29 2.4 SOILS .........................................................................................................................................- 31 2.5 LAND USE ..................................................................................................................................- 31 2.6 WATER USE IN THE RHINE CATCHMENT.....................................................................................- 33 -. 3. CLIMATE AND CLIMATE CHANGE .................................................................................... - 36 3.1 MODELING CLIMATE AND CLIMATE CHANGE ............................................................................- 37 3.2 PROJECTIONS OF CLIMATE CHANGE AND DISCHARGE ...............................................................- 41 3.3 PROJECTIONS OF CHANGES IN SOIL ............................................................................................- 45 3.4 PROJECTIONS OF CHANGES IN LAND USE ...................................................................................- 46 3.5 PROJECTIONS OF CHANGES IN INDUSTRY ...................................................................................- 47 4. THE POSSIBLE IMPACT OF CLIMATE CHANGE ON WATER QUALITY.................. - 48 4.1 PHYSICAL WATER QUALITY .......................................................................................................- 48 4.1.1 Effects of discharge .......................................................................................................... - 48 4.1.2 Effects of water temperature............................................................................................. - 49 4.2 CHEMICAL WATER QUALITY ......................................................................................................- 50 4.2.1 Dissolved oxygen .............................................................................................................. - 50 4.2.2 The major ions .................................................................................................................. - 51 4.2.3 Heavy metals .................................................................................................................... - 52 4.2.4 Nutrients ........................................................................................................................... - 53 4.2.5 Organic micro pollutants.................................................................................................. - 56 4.2.6 PAH’s ............................................................................................................................... - 56 4.2.7 Pesticides.......................................................................................................................... - 57 4.3 BIOLOGICAL WATER QUALITY ...................................................................................................- 58 4.3.1 Effects on dissolved CO2 concentration ............................................................................ - 58 4.3.2 Effects on biological activity ............................................................................................ - 58 4.4 CONCLUSIONS FROM PREVIOUS RESEARCH ON THE EFFECTS OF CLIMATE CHANGE ON WATER QUALITY OF THE RHINE. ..................................................................................................................- 60 4.5 CONCLUSIONS FROM PART ONE ................................................................................................- 61 -. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. -6-. BTO 2006.056(s) 1 September 2006.


(11) Part two: The impact of climate change on the water quality of the Rhine River (Evidence from the past). 5. INTRODUCTION ON PART TWO.......................................................................................... - 66 5.1 SELECTION OF DISCHARGE EXTREMES FROM THE PAST..............................................................- 69 6. GENERAL PARAMETERS ...................................................................................................... - 72 6.1 WATER TEMPERATURE ..............................................................................................................- 72 6.2 SUSPENDED SOLIDS ...................................................................................................................- 78 6.3 OXYGEN ....................................................................................................................................- 83 6.4 CHLOROPHYLL-A ......................................................................................................................- 86 7. MAJOR IONS.............................................................................................................................. - 90 7.1 CHLORIDE..................................................................................................................................- 90 7.2 FLUORIDE ..................................................................................................................................- 91 7.3 BROMIDE ...................................................................................................................................- 92 7.4 SULFATE ....................................................................................................................................- 93 7.5 SODIUM .....................................................................................................................................- 93 7.6 CALCIUM ...................................................................................................................................- 94 7.7 MAGNESIUM..............................................................................................................................- 95 7.8 PROSPECT OF THE MAJOR IONS ..................................................................................................- 96 8. HEAVY METALS AND METALLOIDS ............................................................................... - 100 8.1 THE HEAVY METALS, LEAD, COPPER, ZINC, NICKEL, MERCURY, CHROME AND CADMIUM IN THE RHINE RIVER (LOBITH). ................................................................................................................- 100 8.2 THE METALLOIDS, ARSENIC, SELENIUM AND ANTIMONY IN THE RHINE RIVER (LOBITH). ........- 104 9. NUTRIENTS.............................................................................................................................. - 108 9.1 NITRATE, NITRITE AND AMMONIUM IN THE RHINE (LOBITH)..................................................- 108 9.2 TOTAL PHOSPHATE AND ORTHOPHOSPHATE IN THE RHINE (LOBITH)......................................- 113 10. ORGANIC MICROPOLLUTANTS...................................................................................... - 120 10.1 PAH’S (THE SIX OF BORNEFF AND BENZO(A)PYREEN)..........................................................- 120 10.2 PESTICIDES ............................................................................................................................- 122 10.3 OTHER ORGANICS ..................................................................................................................- 126 11. CONCLUSIONS...................................................................................................................... - 130 REFERENCES .............................................................................................................................. - 134 -. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. -8-. BTO 2006.056(s) 1 September 2006.


(13) LIST OF FIGURES: Figure 1: Three groups of characteristics of water quality with several variables ................ - 18 Figure 2: The climate system involves interactions between atmosphere, hydrosphere, lithosphere, cryosphere and the biosphere. External forcings are the sun and anthropogenic influence. ....................................................................................................... - 20 Figure 3: Water quality in the hydro-ecological system (Domnişoru, 2006). ......................... - 20 Figure 4: Important climate processes, with respect to water quality, on a river catchment scale. ......................................................................................................................................... - 21 Figure 5: Positive and linear relations between Air temperature and Water temperature are often found in statistical analyses for lakes and rivers with values between 0.45 ºC to 1.0 ºC-1 (De Jong, 2006) ................................................................................................................ - 22 Figure 6: Rhine hydrograph, measured near Lobith, of the discharge peak from 1995. (Discharge information from Waterbase, 2005.)................................................................. - 23 Figure 7: The Rhine catchment area and some monitoring locations that are located along the Rhine (Buishand and Lenderink 2004). ............................................................................... - 28 Figure 8. The Rhine catcment area and the main subbasins Aare, Necker, Main and Mosel (Middelkoop et al., 2001). ...................................................................................................... - 30 Figure 9: Present annual discharge regimes of the main tributaries of the Rhine; Aare, Neckar, Main, Mosel (Middelkoop et al., 2001). ............................................................................... - 30 Figure 10: The mean annual discharge of the Rhine river with respect to the input of the subbasins: Aare, Neckar, Main and Mosel (Asselman,1997). ........................................... - 31 Figure 11 Major agricultural regions of Europe. Source: Olesen and Bindi, 2002. Note: 1. Nordic; 2. British Isles; 3. Western; 4. Mediterranean; 5. Alpine; 6. North eastern; 7. South eastern; 8. Eastern (Olesen and Bindi, 2002) ....................................................................... - 32 Figure 12: The mean annual precipitation in the Netherlands of the period 1906-2005 (KNMI, 2006).......................................................................................................................................... - 36 Figure 13: The trends in the number of days with a minimum precipitation of 20 mm, measured at European meteorological stations between 1946 and 2004 (KNMI,2006). - 36 Figure 14: Aletsch (Switzerland) historical length change: 1856 and 2001. (Haeberli and Hoelzle, 2003) .................................................................................................................. - 37 Figure 15: Inter-quartile range (between 75% and 25% percentiles) of different regional models of monthly mean temperature for the months June (cyan), July (blue) and August (black) in Germany (KNMI, Biennial Scientific Report 2003-2004).................................. - 38 Figure 16: The present potential evaporation observed and modeled by HadRM3H (according to Buishand and Lenderink, 2004)........................................................................................ - 39 Figure 17: The mean annual discharge (1961-1995) of the Rhine River at Lobith and the modeled discharge by Rhineflow with the input of a corrected HadRM3H model, by Buishand and Lenderink 2004. ............................................................................................. - 39 Figure 18: The mean annual discharge (1961-1995) of the Rhine River at Lobith and the modeled discharge by Rhineflow with the input of a corrected HadRM3H model, by Lenderink et al. 2004. ............................................................................................................. - 40 Figure 19: the projected absolute temperature change by HadRM3H model for the future (2070-2099) according to Lenderink et al. (2004) ................................................................ - 41 Figure 20: The relative change of precipitation, potential evaporation (Penman) and potential evaporation (scenario H) according to Lenderink et al. (2004). ....................................... - 42 Figure 21: Mean and quantiles of the discharge at Lobith for the two different future scenarios (Buishand and Lenderink 2004)............................................................................................ - 43 Figure 22: The projected annual hydrograph of the year 2050 and 2100 of the Rhine near Rees according to Middelkoop et al. (2001).................................................................................. - 44 Figure 23: The range in differences of the projected discharge of the Rhine between UKHI2100 and HadRM3, according to Middelkoop et al. (2001) and Lenderink et al. (2004) ........ - 44 Figure 24: The effect of an input of effluent on the concentration dissolved oxygen. (Ward and Robinson, 2000) ....................................................................................................................... - 50 Figure 25: Discharges during the selected periods of drought (1976, 1991 and 2003) and their reference periods..................................................................................................................... - 70 Figure 26: Discharges of the selected flood events (1988, 1993, 1995, 1998 and 2003) and their reference periods..................................................................................................................... - 71 The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 10 -. BTO 2006.056(s) 1 September 2006.

(14) Figure 27: The seasonal pattern of water temperature of the Rhine River and discharge.... - 72 Figure 28: Maximum air temperature and '12:00h’ water temperature of the Rhine at Lobith, for the period of 01-07-2003 until 31-06-2004. ..................................................................... - 73 Figure 29: The relation between maximum air temperature and the ‘12:00h’ water temperature of the Rhine at Lobith, for the period of 01-07-2003 until 31-06-2004. ...... - 73 Figure 30: The relation between daily maximum air temperature and water temperature of the Rhine at Lobith for every season (01-07-2003 - 31-06-2004)...................................... - 74 Figure 31: Maximum air temperatures during the period of drought in 2003, when water temperatures reached maximum values. (KNMI, 2006) ................................................... - 75 Figure 32: The relation between water temperature and discharge, and the relation between water temperature and maximum air temperature during the month July (2003). ...... - 76 Figure 33: Evolution of water temperature during five (extreme) flood events. ................... - 77 Figure 34: The concentration of suspended solids and discharge of the Rhine River (Lobith) for the period 1997-2000......................................................................................................... - 78 Figure 35: The relation of discharge and suspended solids of the Rhine River (Lobith) for the period 1997-2000. .................................................................................................................... - 78 Figure 36: Two flood events (1995, 1998) of the Rhine River (Lobith) and the amount of sediment in suspension.......................................................................................................... - 79 Figure 37: Sediment concentrations during the floods of 1995 and 1998 plotted against discharge, resulting in so-called hysteresis loops. ............................................................. - 80 Figure 38: An indication of total discharge and sediment transport during the floods of 1995 and 1998. .................................................................................................................................. - 81 Figure 39: The relations of the discharge peaks of 1995 and 1998 and their sediment concentration before and after the sediment deficit. ......................................................... - 81 Figure 40: The relation of water temperature with dissolved oxygen for the Rhine (Lobith) 2001-2005.................................................................................................................................. - 83 Figure 41: An example of the relation between discharge and dissolved oxygen levels...... - 84 Figure 42: The variability of the relation between water temperature and dissolved oxygen levels for every season. .......................................................................................................... - 84 Figure 43: The extrapolated values of dissolved oxygen concentrations during extreme high water temperatures................................................................................................................. - 85 Figure 44: The concentrations of chlorophyll-A in the Rhine river (Lobith) during the period 2001-2005.................................................................................................................................. - 86 Figure 45: The concentration of chlorophyll-A during the selected periods of drought and their reference years. .............................................................................................................. - 87 Figure 46: An example of the relation between discharge and the concentration of Chloride during the period of 2001-2005 ............................................................................................. - 91 Figure 47: An example of the relation between discharge and the concentration of Fluoride during the period of 1992-1996 ............................................................................................. - 92 Figure 48: The relation between discharge and the concentration of bromide during the period of 2003-2005................................................................................................................. - 92 Figure 49: An example of the relation between discharge and the concentration of sulfate during the period of 2001-2004 ............................................................................................. - 93 Figure 50: An example of the relation between discharge and the concentration of Sodium during the period of 2001-2004 ............................................................................................. - 94 Figure 51: An example of the relation between discharge and the concentration of Calcium during the period of 1987-1989 ............................................................................................. - 95 Figure 52: An example of the relation between discharge and the concentration of Sodium during the period of 1987-1989 ............................................................................................. - 96 Figure 53: The available concentrations of the major ions during (extreme) periods of drought and there reference years....................................................................................................... - 97 Figure 54: An example of the relation between suspended solids and the concentration of lead during the period 2001-2005................................................................................................ - 102 Figure 55: An example of the measured and calculated concentration of Zinc in relation with the concentration of suspended solids, during the floods of 1995 and 1998. ............... - 102 Figure 56: The concentration of lead during the droughts of 1976 and 2003, and its reference periods.................................................................................................................................... - 103 Figure 57: The concentration of arsenic in the Rhine (Lobith) during the period 2001-2005.- 105 The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 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BTO 2006.056(s) 1 September 2006.

(15) Figure 58: The concentration of arsenic in the Rhine during the period 2001-2004. ........... - 106 Figure 59: The seasonal pattern of the concentration of nitrate (mgN/l), nitrite (mgN/l) and ammonium (mgN/l) in the Rhine River (Lobith) for the period 2001 – 2005. ............. - 108 Figure 60: The seasonal fluctuation of nitrate and the relation with water temperature for the Rhine River (Lobith) in period 1997-2000.......................................................................... - 109 Figure 61: The seasonal fluctuation of nitrite and the relation with water temperature for the Rhine River (Lobith) in period 1997-2000.......................................................................... - 109 Figure 62: The seasonal fluctuation of ammonium and the relation with water temperature for the Rhine river (Lobith) in period 1997-2000. ................................................................... - 109 Figure 63: Yearly and seasonal concentrations of nitrate........................................................ - 111 Figure 64: The concentrations of nitrate during the years 2002, 2003 and 2004; zoomed in on the concentration during summer and autumn. .............................................................. - 112 Figure 65: The concentration of nitrate during the flood event of 2003. ............................... - 113 Figure 66: The pattern of the concentration of total phosphate during the period of 2001-2005.114 Figure 67: The pattern of the concentration of orthophosphate during the period of 2001-2005. ................................................................................................................................................. - 114 Figure 68: The relation between suspended solids and total phosphate during a (extreme) flood event ............................................................................................................................. - 115 Figure 69: The relation of suspended solids with the concentration of total phosphate during the (extreme) flood events of 1993, 1995, 1998 and 2003. ................................................ - 115 Figure 70: Yearly and seasonal concentrations of orthophosphate in combination with a linear relation between discharge and the concentration of orthophosphate. ........................ - 117 Figure 71: Yearly and seasonal concentrations of orthophosphate, and a linear relation between water temperature and the concentration of orthophosphate........................ - 117 Figure 72: The concentration of the six of Borneff and Benzo(a)pyreen in the Rhine River during 1992-1996................................................................................................................... - 120 Figure 73: An example of the relation between suspended solids and the concentration of the 6 of Borneff during the flood events. ................................................................................. - 121 Figure 74: Two examples of the development of the concentrations of pesticides in the Rhine River. ...................................................................................................................................... - 123 Figure 75: The concentration of isoproturon in the Rhine (Lobith) during the period 1997-2000. ................................................................................................................................................. - 125 Figure 76: The concentration of MTBE during 2003 and the flood of 2003 in combination with its relations with discharge.................................................................................................. - 128 -. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 12 -. BTO 2006.056(s) 1 September 2006.

(16) The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 13 -. BTO 2006.056(s) 1 September 2006.

(17) Introduction Climate change During the last decennia, world’s air temperature increased, this has led to a changing climate. Temperature increase during the 20th century is well documented on a global and regional scale (IPCC 2001). Recent evidence of increasing air temperatures and a changing climate is the year 2005. For example, according to Sluijter (2006) the mean annual temperature of 2005 in the Netherlands was 10.7 °C, which is 0.9°C higher than long-term annual mean of 9.8°C. The year 2005 takes the fifth place in the warmest years since 1901. In addition, this top-ten of warmest years only consists of years after 1988 and next to that 2005 is the ninth successive year that exceeds mean annual temperature of 10°C. Changing climate affects many natural and anthropogenic processes on earth. The effects of climate change are different for each region and will be visible on local, regional and global scale. Therefore, it is important to understand the complexity and interactions between greenhouse gases, global warming and its effects on the natural and anthropogenic processes. The impact of a changing climate on a river catchment Important processes, involving the hydrological cycle, that are projected to change under recent climate change scenarios are precipitation, evaporation, sea level, glacier melt, river discharge, the groundwater table and so on (IPCC, 2001b; EEA,2004). A lot of research on the effects of climate change on these parameters has already been done. Most of this research was and still is focused on water quantity. For example, it is projected for the Rhine catchment that extremes in both temperature and precipitation will occur more often, resulting in changing river discharges (Kwadijk, 1993; Kwadijk and Rotmans, 1995; Middelkoop, 2000). Furthermore, an increased risk of floods and periods of drought are foreseen (Shabalova et al, 2003; Buishand and lenderink, 2004). However, on a river catchment scale there are far more characteristics that are affected by the process of global warming (Kleinn et al, 2005). For example, increasing levels of carbon dioxide will induce changes in the terrestrial and aquatic ecosystems. Long term changes in land use and urbanisation may lead to other patterns of surface runoff. This in its way will result in a changing water use and chemical loading of surface waters (Domnişoru, 2006). Climate change and water quality Next to the river catchment characteristics, an important parameter that is influenced by climate change and all the above named processes is water quality. According to De Jong (2006), water quality of rivers is most affected during hydrological and meteorological extremes, like floods, heavy rainstorms, and periods of heat and/or drought. However, what the exact consequences of climate change will be for the water quality of the Rhine River is not known. Therefore, research is needed to fill this lack of knowledge; because it is projected that hydrological extremes will occur more often in a future climate. Next to that, it is always important to have enough and clean fresh water for ecology, drinking water production, industrial cooling waters, recreation and human health. In addition, with respect to the water quality of the Rhine River, it is also important when looking to all the water quality standards that are defined in the European Water Framework Directive (WFD). According to this agreement, all surface waters in every European member state must suffice the water quality demands by the year of 2015. Framework and purpose The present report has been written as a subject of the BTO project Risk-analysis effects of climate change. Due to the background of Kiwa N.V., which is focused on drinking water production, mainly water quality standards that are of importance for drinking water production in the Netherlands are in research. Because of the many possible impacts of climate change on water quality, this report tries to find answers on the following questions: The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 14 -. BTO 2006.056(s) 1 September 2006.

(18) Part One 1. 2. 3.. What climate-related and catchment-related processes influence water quality of the Rhine River? How are these climate-related and catchment-related processes affected by climate change? What potential effects will these changes have on the water quality? Part Two. 4. 5.. What has been the water quality of the Rhine River (Lobith) during the floods and periods of drought in the past? What kinds of problems, related to climate change and river water quality, do drinking water production companies face in future?. Structure of the report The report is divided in two main parts, which both contain several sections in which climate change and water quality are the keywords. The first part is a literature review of many potential impacts of climate change on Western-European river catchments and water quality. This part starts with a chapter that gives an overview of climate and water quality related processes on a river catchment scale. Chapter 2 gives a detailed description of the present characteristics and activities of the Rhine catchment that are part of the processes that are affecting river water quality. After knowing the present situation and processes, a summary of several models and their projection of the hydro-ecological system of the Rhine catchment area for the year 2100 is given in Chapter 3. Eventually in Chapter 4, the previous sections are combined and the potential effects of climate change on water quality of rivers, based on literature, are dealt with. However, part one can be skipped by those who are familiar with the potential impacts of climate change on water quality in rivers or if interest is only focused on the effects of climate change on the water quality of the Rhine River. The second part of this report focuses on analyzing fourty-one water quality parameters that are of importance for drinking water production in the Netherlands. These fourty-one parameters can be divided in the following five groups: 1. 2. 3. 4. 5.. Physical and Chemical parameters (4) Major ions (7) Heavy metals (7) + metalloids (3) Nutrients (5) Organic micro pollutants: PAH’s (2), Pesticides (5) and other Organics (8). With respect to the influence of climate change on these parameters, especially hydrological extremes are analyzed. In total, the water quality during five floods (1988; 1993; 1995; 1998; 2003) and three periods of droughts (1976; 1991; 2003) is compared with water quality during mean hydrological periods. Every group of substances is dealt with in a different section, which can be read separately (Chapters 5-10). Where possible, relations have been deduced between discharge and the concentration of substances. In addition, overviews of processes that contribute to the concentrations of substances are given. Next to discharge, potential effects of increasing water temperatures on the concentration of substances are of importance in the context of this report. Eventually conclusions and recommendations about the potential impact of climate change on the water quality of the Rhine River are given in Chapter 11.. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 15 -. BTO 2006.056(s) 1 September 2006.

(19) PART ONE. Potential effects of climate change on the Rhine catchment.. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 16 -. BTO 2006.056(s) 1 September 2006.


(21) 1. Climate and Water quality Water quality is of great importance for a wide range of purposes, including water supply and public health, agricultural and industrial uses. Water quality is also important to preserve aquatic habitats for fish and invertebrates, birds and mammals. Therefore, it is important to investigate the influence of climate change on water quality of the Rhine River. Water quality can be divided into three main groups that are strongly interrelated: physical, chemical and biological water quality (Figure 1). WATER QUALITY. physical. chemical. biological. discharge. dissolved oxygen. phytoplankton. sediment load. nutrients. viruses. temperature. heavy metals. bacteria. ……. ……. ……. standards. Change in water quality. Figure 1: Three groups of characteristics of water quality with several variables Important physical characteristics of water quality are discharge, the concentration of suspended solids and water temperature. River discharge and flow velocity affect chemical and physical water quality; chemically due to the effects of dilution and physically due to its transport capacity. Namely, river discharge leads to the transport of sediments and solids due to its effects on shear stress of sediment particles (Van Bokhoven, 2006). For example, high sediment concentrations are in most cases associated with periods of high discharge. However, in most cases, the amount of sediments carried by a river is several orders of magnitude less than its maximum transports capacity, because the dominant control on suspended sediment concentration is the supply of material to the river and not discharge alone (Van der Weijden, 1992). Suspended solids flow into rivers because of sanitary wastewater and many types of industrial wastewater. There are also diffuse sources, such as soil erosion from agricultural and construction sites. The presence of suspended solids in river water affects aquatic life in several ways. The presence of suspended solids influences turbidity and light penetration, which reduces primary production of aquatic plants and biological activity. Next to that, suspended solids have the capacity to bind many chemicals, like heavy metals or organic micro pollutants (Walling and Webb, 1992). Next to discharge and suspended solids, water temperature is an important physical parameter, because it determines the reaction rates of many biological and chemical processes. One of the most important chemical characteristics of water is the solubility of virtually all substances in water. A few chemical characteristics of water quality are dissolved oxygen and the concentration of various constituents including major ions, nutrients, heavy metals, PAH’s, pesticides and micro pollutants. Chemical processes in natural waters are principally concerned with reactions in aqueous solutions. Many reactions in the aquatic system are reversible, being able to proceed in both directions, and in practice, a dynamic equilibrium will be established between the two opposing reactions. Examples of reversible reactions are The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 18 -. BTO 2006.056(s) 1 September 2006.

(22) the solution of gaseous carbon dioxide in water (Equation 4.4), the solving of calcite, which occurs in many carbonate rocks (Equation 4.5) and the processes involved in eutrophication (Vollenweider, 1974, 1976). Another important group of water quality characteristics is biological activity (Figure 1). Biological activity in open water systems is strongly related to CO2, dissolved oxygen (DO), water temperature, the amount of nutrients and discharge. Biological activity that affects water quality is partly related to Microorganisms. Microorganisms that cause waterborne diseases are several bacteria (e.g. Campylobacter, Salmonelle, Shigella, E. coli, Clostridium botulinum and cyanobacteria), viruses (e.g. noroviruses, enteroviruses and hepatitis A and E viruses), parasites (e.g. Cryptosporidium and Giardia) and fungi, generally known as ‘pathogens’. Further, the presence of too many nutrients, such as nitrogen and phosphorus, can stimulate algal blooms and result in reduced water clarity. Especially pathogens that cause waterborne diseases, like the Cyanobacteria or the bacteria that cause botulism, are important threats to water quality. Algae blooms usually consist of a single species of algae, typically a species undesirable for fish and other predators to consume. Unconsumed algae sink and decay, depleting the oxygen required by other plants and benthic organisms to survive. The origin of waterborne pathogens are both point and diffuse sources of human and animal faeces which enter surface waters by discharges of wastewater, by runoff from the land and by seepage of contaminated groundwater (Aitken, 2003; Ferguson et al., 2003; Schijven and Husman, 2005). Pathogens are spread through contaminated drinking water, exposure to contaminated water or secondarily through vectors (e.g. fishes, mosquito; Zell, 2004) or food contaminated with water of poor quality (Rose et al.. 2001). Many processes and reactions influence the characteristics of individual physical, chemical and biological parameters. Therefore, the physical, chemical and biological parameters are related to some kind of standard. Without this standard, it is impossible to determine water quality, because ‘water quality’ is a subjective term. The interactions between these parameters are complex and depend in some way on the climate system (Ward and Robinson, 2000). The definition of a climate system is: “a system, which involves the natural interactions (internal forcing) between atmosphere, hydrosphere (oceans, lakes, and rivers), lithosphere (land), cryosphere (ice) and the biosphere (life).” External forcing is supplied by the sun as well as by anthropogenic influences (Airweather, 2006) (Figure 2). A climate system can be projected on a large variety of temporal and spatial scales. On a scale of a river catchment, it is common to use the term of a regional climate system. According to Figure 2, a river is part of the hydrological system. The fact that all sorts of organisms live in a water body like a river, makes it part of an ecological system as well. A more general term that is used for the combination of the hydrological and ecological system is the “Hydro-ecological system”. Based on Arnell (1994), Domnişoru (2006) developed a diagram in which water quality is related to the most important parameters of the hydroecological system (Figure 3). According to Figure 3, water quality depends on nine characteristics of the hydro-ecological system, respectively greenhouse gasses, air temperature, rainfall and evaporation, sea level, land use, the aquatic ecosystems, the terrestrial ecosystems, glacier and snow pack dynamics, and the quantity of fresh water.. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 19 -. BTO 2006.056(s) 1 September 2006.

(23) Figure 2: The climate system involves interactions between atmosphere, hydrosphere, lithosphere, cryosphere and the biosphere. External forcings are the sun and anthropogenic influence.. GREENHOUSE EFFECT. •. INCREASE IN AIR TEMPERATURE. Change in rainfall and evaporation. Change in sea level Change in aquatic ecosystems Change in land use Change in terrestrial ecosystems Change in glacier and snowpack dynamics. Change in water quality Change in water quantity Figure 3: Water quality in the hydro-ecological system (Domnişoru, 2006).. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 20 -. BTO 2006.056(s) 1 September 2006.

(24) Besides the hydro-ecological system, the social-economical system, which is influenced by the policy of international, national and local governments, affects water quality due to anthropogenic input of all kind of pollutants (Klein, 2005). For example, industrial and domestic waste flowed untreated into the Rhine River, for decades. The river was one of Europe’s most repelling waste dumps. Fish disappeared and it was dangerous to swim in. For these reasons, governments changed their policy and the International Commission for the Protection of the Rhine (ICPR) was established in 1950 as a permanent intergovernmental body to handle general pollution issues. In addition, Figure 4 summarizes the combination of the hydro-ecological and socialeconomical system, on a river catchment scale. CO2. EU Policy. Air temperature Precipitation and Evaporation. Soil type, Land use and Industry. Snow pack/ Glacier. Terrestrial ecosystem. Runoff. Water temperatuur. Sea level rise. Discharge. Load. River Physical. Chemical. Biological. Figure 4: Important climate processes, with respect to water quality, on a river catchment scale. As shown, some processes are more important than others; processes that have a direct link with water quality, and processes that are the most important on a river catchment scale are presented with thick arrows. The following paragraphs of this chapter, will deal with the processes given in Figure 4 in general. Later on, in chapter 3 the possible impacts of climate change on these processes in the Rhine catchment are described.. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 21 -. BTO 2006.056(s) 1 September 2006.

(25) 1.1 Water temperature It is generally accepted that increased and still increasing levels of carbon dioxide (CO2) and other greenhouse gasses cause global warming (Kundzewicz and Somlyody, 1997; IPCC, 2001; EEA, 2004). Increasing air temperatures affects water quality due to its influence on water temperature. Water temperature affects biological activity and chemical reactions in an aquatic ecosystem. For example, the productivity, evolution, distribution and ecology of aquatic organisms are fundamentally affected by water temperature. Furthermore, the toxicity of contaminants, the efficacy of water treatment, the occurrence of tastes and odors, the probability of waterborne diseases, the processes involved by cooling water, and the formation of ice in navigable waterways, are all affected by water temperature. Therefore, water temperature is one of the most important physical characteristics of fresh water that determines water quality (Walling and Webb, 1992). According to Ozakie et al. (2003) water temperature is linearly and positively correlated with air temperature. This is also found by many statistical analyses for both lakes and rivers. According to Figure 5, the gain of this relation varies between 0.45 and 1.0 for yearly averages (e.g. Walling and Webb, 1992; Fukushima, et al., 2000; Ozakie et al., 2003; Caissie et al., 2005). Therefore, water temperature depends on air temperature. In addition, even when air temperature is measured, at several tens of kilometers from the river water temperature monitoring site, the linear functions given in Figure 5 are often characterized by high levels of explained variance (Mohseni et al., 1998; Webb et al., 2003). 1.0 ºC/ºC. 0.45 ºC/ºC. water temperature [ºC]. 1. 0,75. 0,5. 0,25. 0 0. 0,25. 0,5. 0,75. 1. air temperature [ºC]. Figure 5: Positive and linear relations between Air temperature and Water temperature are often found in statistical analyses for lakes and rivers with values between 0.45 ºC to 1.0 ºC-1 (De Jong, 2006) Besides the linear air-water temperature gradient, also non-linear relations between air- and water temperature are found. For example, the effect of air temperature on water temperature, defined by hourly or daily data, decreases for some rivers (Mohseni et al., 1999; 2002; Webb et al., 2003). This decreasing influence of air temperature on hourly or daily water temperature often results in a S-shaped air-water temperature relation (Mohseni et al., 1999). Possible explanations of this S-shaped air-water temperature relation are the presence of water temperatures below 0 ºC due to ice cover, and water temperatures above 20 ºC leading to increasing evaporation rates. Increasing evaporation rates in combination with enhanced long wave back radiation, results in cooling water bodies. Nevertheless, Webb et al. (2003) concluded for rivers in South-west England that data on weekly or yearly basis, can be plotted as linear relations.. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 22 -. BTO 2006.056(s) 1 September 2006.

(26) Next to the relation between air temperature and water temperature, water temperature can show a negative relation with river discharge (Webb et al., 2003). A higher discharge, e.g. during storms, floods or snow smelt, increases the thermal capacity and makes a river less sensitive to air temperature. On the other hand, low discharges, e.g. during droughts, make a river more sensitive to air temperature, increasing the diurnal variation in water temperature (Walling and Webb, 1992). Next to the total discharge, the contribution of groundwater to this total discharge is important for water temperature. Groundwater decreases the diurnal temperature variation, it warms the water during winter and it cools the water during summer.. 1.2 River discharge and sea level rise Differences in river discharge influence water quality by its effects on the transport and dilution of water quality related substances. River discharge is the result of a combination of catchment characteristics and climatic forcing. Especially, precipitation intensity, precipitation pattern, the rate of evaporation and the presence of glaciers are important characteristics that determine river discharge, because they have an effect on the amount and availability of freshwater. However, also catchment characteristics, like geology, soil type, land use and human activity translate the precipitation excess into a certain river type with a unique temperature and discharge regime. On a short time scale, the main sources that contribute to river discharge are short-term surface and subsurface runoff (Webb and Walling, 1992). These short-term processes mainly depend on precipitation characteristics (intensity, distribution), topography, infiltration rate, soil moisture content and groundwater level (Burt, 1992). The various interacting processes that involve the transformation of precipitation excess into discharge are complex and spatially and temporally variable (Beven, 2001). On a short time scale, precipitationdischarge transformation in a river catchment is best analyzed when a flood occurs. Flood events are best presented by a hydrograph. A hydrograph is a graph showing stage, flow velocity or other properties of water with respect to time (Langbein and Iseri, 1995). The shape of the hydrograph is unique for a catchment and is the result of the interaction between the catchment characteristics and the climatic forcing. It therefore contains valuable information on catchment processes. An example of a hydrograph of the Rhine River near Lobith is given in Figure 6.. Hydrograph high discharge Lobith, 1995 14000 LN Q 9,6. 12000. 9,4. LN Q. 9,2. 10000. 9 8,8 8,6 8,4 8,2. 8000 m3/s. 8 1995-01- 1995-01- 1995-02- 1995-02- 1995-02- 1995-0226 31 05 10 15 20. 6000. Direct Flow 4000. 2000. Base Flow. Hydrograph high discharge 1995 Lobith Base-Directflow seperation line. 19 -1 -1 99 5 21 -1 -1 99 5 23 -1 -1 99 5 25 -1 -1 99 5 27 -1 -1 99 5 29 -1 -1 99 5 31 -1 -1 99 5 2219 95 4219 95 6219 95 8219 95 10 -2 -1 99 5 12 -2 -1 99 5 14 -2 -1 99 5 16 -2 -1 99 5. 0. datum. Figure 6: Rhine hydrograph, measured near Lobith, of the discharge peak from 1995. (Discharge information from Waterbase, 2005.) The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 23 -. BTO 2006.056(s) 1 September 2006.

(27) It is the hydrograph of second highest discharge peak of the 20th century, which had a maximum discharge of 11885 m3/s. It was observed from 22-01-1995 until 10-02-1995 and it took the river 10 days to reach maximum discharge. In total, 1.26*E10-m3 water of which 6.83*E09-m3 as direct runoff and 5.72*E09-m3 as base flow came to discharge (Figure 6). In addition, this flood wave resulted as an outcome of the following conditions (Chbab, 1996): • • • •. During the first week of January, circumstances were wintry and precipitation fell especially in the form of snow. From 10 to 20 January, snowmelt resulted in saturated subsoil in large parts of the catchment area. From 21 January, the weather changed and the soft western currents led to large quantities of rainfall. In this period, an average of 100 mm precipitation fell all over the Rhine catchment area. This is about twice the normal rain quantity in January. At the same time, the western currents were accompanied by a strong increase in temperature. Therefore, precipitation and snowmelt caused extreme discharges in most of the tributaries such as Main, Moselle, Sieg, Ruhr and Lippe.. Further more, floods take place regularly on the Rhine River, especially during winter and early spring. Three elements account for this (Chbab, 1996): 1. 2. 3.. Snowmelt occurs due to relatively high temperatures mostly after winter conditions. There must be a large quantity of precipitation that is spread over the different areas of the river catchment. The subsoil in the basin must be saturated or frozen in such a way that (rain) water cannot be stored, but will be discharged quickly.. Mean discharge is the result of the difference between rainfall and evaporation in combination with the contribution of snow- and glacier melt. Glaciers in mountainous areas exert a considerable influence on catchment hydrology and climate, by temporarily storing water as snow and ice (Jansson et al., 2003). Runoff from a glacier-free catchment is dominated by precipitation whereas glacierized basins are energy dominated (Hock, 2005). The contribution of snow- and glacier melt is important during periods of droughts. During hot, dry periods, when precipitation is lacking and evaporation rates are high, glaciers produce most water. For example, the contribution of Swiss mountains to the flow of the Rhine in the Netherlands is disproportionally large, varying seasonally from 30% in winter to 70% during summer. Similarly large contributions to the annual flow are observed in the Rhone River (32% of the mountain area contributes 47% to the lowland flow) and the River Po (32% of the mountain area contributes 56% to the lowland flow (Swissworld, 2006). Besides the contribution of glaciers to the discharge of rivers, the contribution and availability of melt water is of major importance for water quality. Without this melt water river discharge will be reduced to minimum discharges during droughts and these minimum discharges affect water quality the most (De Jong, 2006). In addition, glaciers control sea level. If the small glaciers (all the glaciers without the Greenland and Antarctic Ice Sheets) melt completely, sea level would probably rise 0.5 m or more as a result of temperature expansion (IPCC, 2001a). Such a rise will accomplish a rise of the drainage base, decreasing the outlet capacity of rivers. This increases the inundation risk of floods and causes salt-water intrusion and salinization, which deteriorates water quality of groundwater and surface waters in the coastal zones (EEA, 2004).. 1.3 Chemical loadings According Figure 4, soil type, land use and industry, directly and indirectly influence water quality by their input of chemicals. For example, the input of industrial wastewaters will directly affect water quality. On the other hand, other landuse types will affect water quality indirectly at the time chemicals that are accumulated on the soil surface flow away by surface runoff or at the time, they dissolve in groundwater. These examples seem to be very clear, The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 24 -. BTO 2006.056(s) 1 September 2006.

(28) however, the relation of soil, land use and industry with water quality is far more complex and many processes are involved. One of the most important characteristics of soil in relation to water quality is the soil moisture content. It not only influences the terrestrial ecosystem but it also defines the degree of infiltration and surface runoff (Harvey, 2000). The soil moisture content has an influence on the rate of actual evaporation, groundwater recharge and runoff generation (IPCC, 2001). The soil moisture content depends on the proportion of soil organic matter (Olesen and Bindi, 2002), mineral constituents and soil structure, because these parameters define the water holding capacity and the infiltration capacity of the soil (Tao et al., 2005; IPCC, 2001; O’Neal et al., 2005). Another important aspect of soil is soil structure, because it determines the flow paths through the soil and on the surface, which affects the transport of chemical load to rivers. Soils with high groundwater levels and low infiltration capacity, like clay, are almost immediately saturated during precipitation. This leads to quick surface runoff. On the other hand, when groundwater levels are low or soils with high infiltration capacity are present, most precipitation will infiltrate into the soil. Besides the interaction between the quantities of precipitation and groundwater, soil characteristics itself affect water quality by the weathering of rocks and the erosion of sediments (Ward and Robinson, 2000). Not only the chemical reactions and their results caused by rock weathering, but also the source-area of the sediment affect water quality in rivers. For example, in a case study of two medium floods in April and May of 1994 in the Rhine River, it was possible to determine the source-area of sediment particles (Zwolsman et al., 2000). The first flood originated from rainfall in the central part of the Rhine, and was mainly fed by the tributaries Neckar, Main and Mosel (See section 2). The second flood was mainly fed by rainfall in the Alps, with only a minor contribution from the rest of the catchment. Material that erodes from the Alps is richer in calcium carbonate than material that erodes from the central part of the catchment. Therefore, the relative concentration of calcium during the May flood was significantly higher than during the April flood. The Barium-contents of the suspended matter showed the opposite effect (Zwolsman et al., 2000). The impact of land use on water quality is strongly related to human activities, and, although more restricted, to climate and soil type. Land use influences interception of precipitation, it determines the rate of evapotranspiration to a large extent, it estimates the ratio between total infiltration and surface runoff, and it has an effect on the amounts of pollutants that are transported during surface runoff (Grabs, 1997). Therefore, land use is a very important characteristic that affects water quality. Land use in Europe is categorized into urban areas, forestry and agriculture (Niehoff et al., 2002). Especially, agriculture is an important factor in determining water quality. It supplies pollutants, such as nitrates, phosphate, pesticides, herbicides and heavy metals. Due to this, the agricultural sector is the most important component in causing eutrophication and pollution of the terrestrial and aquatic environment. Eutrophication is the process of enrichment of surface waters by high nutrient loads, causing abundant algal growth, which in turn reduces the chemical water quality of lakes and rivers (Van der Molen, 1999; Scheffer, 1998; Søndergaard et al., 2001). Next to that, agricultural land use is an important element in the chain of rainfall – runoff relations in the Rhine basin. During the last decades, investments in land drainage, external water supply and large-scale use of biocides and fertilizers have lead to an increase of agricultural production, but also to a faster response of runoff to rainfall and thereby an increase of flood risks (Klein et al., 2005). Next to soil characteristics and land use, industries are important factors affecting water quality (Figure 4). Along rivers, many industrial activities are taking place; Chemical industry, food processing industry, textile industry, metal industry, rubber industry, hydropower industry, petrochemical industry, refineries, shipbuilding and several other services. All these industries benefit from the navigational properties of a river, but also a large volume of river water is used for cooling purposes, chemical process water and as dump of wastewater. For example, industrial powerplants use river water for cooling purposes, which increase river water-temperature. Increases in water-temperature affect the environment by disturbing the The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 25 -. BTO 2006.056(s) 1 September 2006.

(29) natural conditions for ecosystems resulting in a change in water quality. Besides an increase of water temperature, industry is a source of chemicals, heavy metals and organic micro pollutions, which will all affect the water quality.. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 26 -. BTO 2006.056(s) 1 September 2006.


(31) 2. The Rhine catchment area and present climate The Rhine plays an important role in West European society. It affects economy and environment of Western Europe. With a population of 50 million inhabitants and an average density of 270 persons/km2, the Rhine basin is densely populated, especially since a significant part of the population is concentrated in a number of major cities along the river or its larger tributaries (Speafico & Kienholz, 1996). To relate the very complex interactions between climate change and water quality in the Rhine catchment area, it is necessary to have an overview of the main characteristics. This section describes the main characteristics of topography, present climate, discharge, soil, land- and water-uses.. 2.1 Topography The Rhine is the longest river (1320 km) in Western Europe stretching from the Swiss Alps to the Dutch coast of the North Sea. The catchment size is 185 000 km2. The catchment consists of nine countries that contribute to the discharge of the Rhine (Middelkoop et al., 2001), Figure 7.. Figure 7: The Rhine catchment area and some monitoring locations that are located along the Rhine (Buishand and Lenderink 2004). In general, the Rhine basin can be characterized by three different areas with a distinguished topography (RIZA, 2000 & Dieperink, 1997): • • •. Alpine Rhine and High Rhine Upper Rhine and lower Rhine Delta Rhine. The Alpine and High Rhine The Rhine originates in the Gotthard Massif (Swiss Alps) at an elevation of approximately 3,400 m above sea level. It results from the confluence of two small rivers, the Hinterrhine and Vorderrhine. It then continues its course and flows through the Bodensee. This part of the Rhine is called the Alpine Rhine, of which about 400 km2 is covered with glaciers (Grabs, The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 28 -. BTO 2006.056(s) 1 September 2006.

(32) 1997). The Alpine Rhine basin has a complex topography, the largest alpine subbasin is the Aare basin with an area of 18000 km2 (Kleinn, 2005). The stretch from the Bodensee down to the city of Basel is the High Rhine. The Upper and Lower Rhine The Upper Rhine is the stretch of the river between Basel and Bingen at the Rhenish Slate Mountains. The Upper Rhine flows between two hill ranges, the Vosges Mountains (France) and the Black Forest (Germany), both reaching up to about 1300 m (Kleinn et al., 2005). This part of the Rhine was originally wide and dynamic, consisting of multiple channels and meanders. Eventually, the river was regulated, mainly to stop frequent flooding. The part of the Rhine in the Rhenish Slate Mountains is known as the Middle Rhine, and further downstream to the German - Dutch border is called the Lower Rhine (Klein et al., 2005). In the lower Rhine, three larger subbasins feed the Rhine: Neckar (13000 km2), Main (25000 km2), and Mosel (27000 km2). While the Mosel basin reaches up to 1300 m in the Vosges Mountains, both the Neckar and the Main basin are lowland catchments (below 1000 m) (Kleinn et al., 2005). The Rhine delta Near the German-Dutch border, the Rhine changes from an eroding to an accreting river. During the last 10000 years, the Rhine has accumulated his sediment in this area, meaning that the Rhine Delta lies almost totally in the Netherlands. Just after entering the Netherlands, the river divides into three river branches: the Waal, the Nederrijn and the IJssel. Near the mouth, the Rhine system mixes with the river Meuse and than flows into The North Sea.. 2.2 Present climate in the Rhine catchment The Rhine catchment is located in a zone of temperate climatic conditions, characterized by frequent weather variations. In the present climate of western central Europe, the annual rainfall is mainly dependent on eastward moving Atlantic depressions. In the Alpine area up to 2000 mm/year of precipitation is received. On average, this precipitation falls as snow above 3050m and during the winter season. The German and French parts of the Rhine catchment are characterized by a temperate oceanic climate, which is gradually changing into a more continental climate from northwest to the east and southeast. The annual rainfall in this part of the catchment ranges from 1100 to 570 mm/year. The Netherlands, which include the Rhine delta, have a temperate oceanic climate, influenced by the North Sea and the Atlantic Ocean. Rainfall reaches an annual average of 800 mm/year and is evenly distributed over land (Pfister et al., 2004).. 2.3 Discharge characteristics To describe the mean discharge characteristics of the Rhine, it is important to know which sub-catchments contribute to the total discharge of the Rhine. The four most important subbasins that contribute to the discharge of the Rhine River are: Aare (Alpine), Neckar (Germany), Main (Germany) and Mosel (Germany and France) (Figure 8). The annual discharge of the Aare peaks between May and July, when a lot of snow melts. In general, it reaches maximum discharges of around 400 m3/s. Annual low discharge (200 m3/s) occurs in the months December and January, (Figure 9) (Middelkoop et al., 2001). The Neckar flows into the Rhine near Maxau. The annual discharge of the Neckar (measured at Rockenau) has an average of about 125 m3/s, it peaks in the months January, February and March (215 m3/s) and during the months September and October the annual discharge is lowest (50 m3/s) (Figure 9). Near Mainz, the river Main flows into the Rhine River. The Main River has an annual discharge that varies between 75 m3/s (in October) and 325 m3/s (in February) (Figure 9). Near Andernach the Mosel flows into the Rhine. The annual discharge of the Mosel measured at Cochem, peaks in the months January, February and March with an average discharge of 650 m3/s, and a minimum discharge of about 50 m3/s is common in the months September and October (Figure 9).. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 29 -. BTO 2006.056(s) 1 September 2006.

(33) Eventually, the total annual discharge cycle of the Rhine River with the contribution of the rivers Aare, Necker, Main and Mosel is given in Figure 10.. Figure 8. The Rhine catcment area and the main subbasins Aare, Necker, Main and Mosel (Middelkoop et al., 2001).. Figure 9: Present annual discharge regimes of the main tributaries of the Rhine; Aare, Neckar, Main, Mosel (Middelkoop et al., 2001).. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 30 -. BTO 2006.056(s) 1 September 2006.

(34) Figure 10: The mean annual discharge of the Rhine river with respect to the input of the subbasins: Aare, Neckar, Main and Mosel (Asselman,1997). According to Baumgartner et al. (1983) the contribution of the total alpine subbasin, to the total discharge of the Rhine River varies between 30% (in winter) to 70% during summer. On average, the contribution of this area is about 50% (1000 m3/s) of the total discharge. Therefore, this Alpine region plays an important role in the annual discharge cycle of the Rhine River. The annual discharge of the Rhine river at Rheinfelden (just downstream of the Alpine region) peaks in the months June, July and August with an average high discharge around 1300 (m3/s) and a low discharge during the months December and January (600 m3/s), Figure 10 (Middelkoop et al., 2001). At the Dutch- German border, near Rees, the average annual discharge is approximately 2,200 m3/s, with a maximum discharge of 12,600 m3/s (1926) and a minimum discharge of 620 m3/s (1947) (RIZA, 2000). In the Upper Rhine, floods are most frequent during spring, since they are generated by snowmelt in the Swiss Alps. In the Middle Rhine, floods are generally observed during the winter semester. In the lower Rhine, most floods are restricted to the winter semester.. 2.4 Soils Sediment transport in the Rhine River is mainly derived from rock weathering, soil formation and soil erosion on the valley side slopes and interfluvial areas of the basin. Loessial and loamy soil types mainly dominate the Rhine basin (Ploeg, 2000). Therefore, mainly clay and silt flow off as overland flow contributing to the transport of suspended sediment in the Rhine River. In addition, special sources of fine sediment are the wind blown loess deposits, which occur in parts of the Rhine area. In the Alpine part of the basin, also mass movements may contribute to the total sediment load of the Rhine River. Water quality is affected by suspended sediment transport because sediments react with, and bind heavy metals, nutrients, PAH’s and micro pollutants. At the point where the Rhine leaves the Bodensee, it carries an average annual sediment load of 3 million m3 as a results of soil erosion. One third of this reaches the North Sea, the rest is deposited in the rivers and floodplains (RIZA, 2000). Therefore, alongside the Rhine River, many areas in the floodplains are contaminated with pollutants as a result of ongoing sedimentation of contaminated fine silt and clay particles (Klein et al., 2005).. 2.5 Land use Under present-day conditions, about half of the total area of the Rhine basin is in use for agriculture, approximately one third is forest, 11% is built-up area including industry, and the remainder consists of surface water (Klein et al., 2005). As already mentioned in paragraph 1.3, agriculture and industry are important parameters with respect to water quality.. The impact of climate change on the water quality of the Rhine River @ Kiwa Water Research. - 31 -. BTO 2006.056(s) 1 September 2006.